JPH04502127A - Stretch forming method and device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] Stretch forming method and device Technical field The present invention relates to a method and apparatus for forming elongated hollow or solid articles, and has particular features. A method and apparatus for consistently forming precise spatial dimensions of elongated extruded products It depends.

Background of the invention A considerable number of working parameters and conditions exist in various metal forming methods. , whereby the finished product exhibits dimensional variations. In certain methods, the dimensions Variations in method may be tolerated, but variations in dimension may be tolerated in other methods. Therefore, subsequent metal finishing work is required.

For example, in an extrusion process, a heated metal ingot or billet is Pressure is passed through a die opening to form elongated items such as timber, tubing or angles. Forced to flow under force. In a typical aluminum extrusion process, The output product is forced through the die with a force in the range of 500 to 15,000 tons. Ru. Extrusions can be heated in an oven at temperatures between about 148°C (300°F) and about 648°C (1200’F). It comes out of the die of the extrusion press at an elevated temperature. In-line solution heat treatment Solution heat treatment is applied to the extruded product during the manufacturing process or by a separate solution heat treatment process. It is common practice to process and harden the material. Such an extruded product has a length of about 45 m (1 can be made in a variety of lengths, including lengths exceeding 50 ft), and in a variety of cross-sectional shapes. may exist.

Considering the operating parameters of the extrusion process including pressure, temperature, die conditions and product length. , and considering the effects of subsequent heat treatment and quenching, the cross section of the extruded metal product is It is understandable that there are considerable dimensional variations with respect to the length of the product and with respect to the length of the product. Ma In addition, such dimensional variations exist from product cycle to product cycle and from extrusion run to process. It is also understandable that there are Therefore, the product must be kept within acceptable dimensional tolerances. It is often necessary to carry out subsequent metal finishing operations to ensure that the push Dimensional variations in drawn metal products include bending, roll straightening, and hammering. Some traditional metal finishing operations cannot be easily modified. Such existence Springback is a major concern in modern metal finishing operations. That's it Springback can be very serious, especially in products with considerable dimensional variations. extreme and therefore such conventional metal finishing operations are inappropriate.

Preforming methods and equipment provided a way to finish the shape of articles such as extrusions. . The tolerances currently allowed for such products are particularly limited for extrusions with thin walls. as specified by the Aluminum Association. products are excluded from certain strict uses. If the dimensional deviation is reduced If so, the product can be used in an increased number of applications where size is critical.

Furthermore, the dimensional quality of the product in existing applications is dramatically increased.

Prior techniques to improve dimensional tolerances and minimize dimensional variations in finishing operations Despite attempts at this technique, further improvements are expected. Therefore, from the nominal value In order to minimize the cross-sectional and longitudinal dimensional deviations of elongated products such as extrusions, A stretch forming method and apparatus that results in a finished form is desired.

Disclosure of invention The present invention provides an improved method and apparatus for finish forming elongated metal extrusions. It can be summarized as: This method applies a partial amount of axial tension to exceed the yield strength of the extrudate. The process includes applying force to an elongated metal extrusion. The external forming die or the external surface of the extrusion Applied to the surrounding area. The die has a finished cross-section for extrusions. Draw a working surface that roughly corresponds to the shape. While maintaining tension, the die extends the entire length of the extrudate. It moves forward along the same lines. - In the recommended practice, the inner surface of the extrusion is In cooperation with the surface forming die, the internal forming die is used to obtain Ftl and t1.

Among the advantages of the present invention is the ability to produce elongated metal extrusions with minimal dimensional variability. A method of molding is provided.

Another advantage of the present invention is that extrusion in a process with minimal springback To provide a method and apparatus for performing consistent spatial dimensional modification on a product. Ru.

One object of the present invention is to provide a finish that can be easily used in-line with the extrusion process. An object of the present invention is to provide a molding method.

One feature of the method of the invention is that the finished product can be processed without creating significant residual stresses in the product. The extruded product is molded to the desired dimensions.

Another feature of the invention is that the extruded aluminum product is manufactured by the American Aluminum Association. better than the dimensional tolerances currently accepted by the European Aluminum Standard Therefore, the dimensional tolerances are within the currently accepted ('') tighter dimensional tolerances. It is something that can be shaped.

Another advantage of the present invention is the production of extrusions within previously unachievable tolerances and What is provided is something that allows the use of extrusions in dimensionally critical applications.

These and other objects, features and advantages of the invention will be apparent from the following description and accompanying drawings. will be more fully understood and appreciated when reference is made to .

Brief description of the drawing Figure 1 shows the as-extruded, solution heat-treated and hardened strip. 1 is a partial perspective view of a long hollow metal extrusion; FIG.

FIG. 2 shows the elongated hollow metal extrusion of FIG. 1 after stretch forming according to the present invention. FIG.

Figure 3 shows the extruded microstructure in the as-extruded state and the solution heat treated (quenched) state. 1 is a partial perspective view of a long solid metal extrusion; FIG.

Figure 4 shows the m-long solid metal extrusion of Figure 3 after stretch forming according to the invention. FIG.

FIG. 5 is a perspective view of the external forming die.

FIG. 6 is a schematic elevational view showing the assembly of the device of the present invention.

Figure 7 shows a somewhat complicated structure in the as-extruded and heat-treated (quenched) state. 1 is a partial perspective view of an elongated solid metal extrusion in shape; FIG.

FIG. 8 is a partial perspective view of the elongated extrusion of FIG. 7 after stretch forming according to the present invention; It is a diagram.

Mode of carrying out the invention The present invention is a method for forming elongated products such as extruded products into final dimensions with strict dimensional tolerances. Law and equipment oriented.

Due to the number and complexity of various operating parameters including quenching for extruded products , typically extrudates are characterized by wide dimensional variability. Such dimensional changes dynamics, lack of consistent control of extrusion and quenching processes, tooling and maintenance due to nonce and thermal distortion. Traditional rework procedures to correct dimensional variations are , both expensive and inefficient. The present invention relates to longitudinal cross-sections of elongated extrusions with linear lengths and Overcomes the aforementioned drawbacks by providing a method to consistently correct for transverse dimensional variations do.

Straight length extrusions include both complex and simple shapes and range from complex hollow to simple. Contains simple solid structures. Figure 1 shows a relatively simple hollow extrusion with four walls. O is illustrated. FIG. 3 illustrates a relatively simple solid (open) chevron extrusion 30.

Preferred extrudates of the present invention are extrudates with thin walls, i.e. walls of less than about 4+ nm. Thickness, such as extruded products with thick walls between extrusion and quenching. This includes those that typically cause a lot of distortion.

However, it is not limited to them. Such preferred extrudates have high ductility extruded products, such as 6000 series aluminum alloys, and 2000 series and 7000 series harder aluminum alloys as well as aluminum lithium Including aluminum alloys. Recommended for applications in the automotive and aircraft industry and of the present invention Extrudates that can be stretch-formed by the method 2024.6061.6063.6 Includes 009 and 7075 aluminum alloys.

However, it is not limited to them.

In the method of the invention, the elongated extrudate is stretch formed to final dimensions. Start processing The current workpiece is an extrusion after the product has typically been solution heat treated. Like that The extrudates are elongated and can extend to lengths in excess of about 45 m (150 ft).

Relatively long extrusions minimize end scrap losses as a percentage of total finished product; Therefore, it is desirable. In the extruded and hardened state, the extrusion will not warp or bow. exhibiting shapes, corrugations, bulges, or off-dimensional, distorted lateral surfaces as shown in Figure 1. The cross-sectional condition is presented as a result of the variables in the extrusion and quenching process. In Figure 1 In addition to off-dimensional cross-sectional shapes as shown, the extrusion may be arcuate, corrugated, or twisted. It is incomprehensible that this should appear over its entire length. Such an extrudate is first subjected to axial, ie longitudinal, pulling in the method of the invention. Must be under tension. In the present invention, the elongated extrudate is stretch-formed. sent to the device. The extrusion is fitted with a suitable gripper mechanism, such as that shown in Figure 6. A fixed gripper 70 and an adjustable gripper 72 typically hold the longitudinal ends of the extrusion. Produced in parts. In the present invention both grippers may be adjustable. It should be understood that - In the recommended embodiment, the gripping surface of the gripper mechanism is manufactured Fits the contour and shape of the extrusion to strengthen it. Such production equipment is custom-made. of the extrudate, including the end portion called the gripper and entering with respect to the gripper device. Ensuring that a substantially uniform tensile force is applied across the entire length and cross-section. and helps to minimize or eliminate adverse end effects. system To further enhance the gripping mechanism, the retaining surfaces of the gripper mechanism have a treated finish, e.g. knurling. with a serrated or serrated finish, or rubber, rubberized or elastomeric or heavy A coalescent surface treatment may be applied. Some sawtooth structures are created when tensile forces are applied to the work piece. It works to increase the production effect as the production progresses.

The production mechanism can be worked by any method, but hydraulic or pneumatic tightening devices is recommended. The extrusion may be fixedly secured at one end and the other end may be fixedly secured at the sixth end. It can be tensioned to provide the required axial tension as shown. alternatively , simultaneously so that both longitudinal ends of the gripped extrusion provide the required axial tensile force. can be pulled to The axial tensile force is typically a hydraulic system as the source of the tensile force for the force F. Provided using a cylinder or mechanical drive means.

What is required in the method of the invention is that the two ends produced are extruded between them. The parts of the item are subjected to sufficient force, typically forces opposing each other in opposite longitudinal directions. , by applying an axial tensile force, i.e., a longitudinal force. It is. A force applied in one direction holds one end of the extrusion in a fixed position while pushing It also provides an axial tensile force that is greater than or equal to the yield point of the exhibit. It is to be understood that

The axial tensile force is equal to or exceeds the material's yield strength, i.e. its elastic limit. It must be sufficient for

The yield strength depends on the metallurgy of the material, i.e. the processing and tempering that has already taken place regarding alloy deformation. It will be understood by those skilled in the art that it is a function of . Furthermore, the yield strength and The amount of force required to equal or exceed the be. Typical yield strengths for extruded aluminum products are: Nialuminum alloy tempered yield strength (ksi) 6009 T4 24 6009 T6 41 8061T421 6061 T6 40 7075 T6 73 2024 T4 47 As will be explained in detail below, the forming of the extrusion in the present invention Eliminate irregularities in cross-section and length, including warping, twisting, and bending. the As such surface distortions are removed, the longitudinal length of the extrudate typically increases.

Also, in the supply of axial tensile force, the length of the extrusion is determined by the permanent longitudinal elongation. Increase by at least about 0.25%. Enough for all elements of 6000 alloy products The permanent longitudinal elongation that occurs when a tensile force is applied is typically less than about 3%. For some alloys it is on the order of 0.5%. For harder alloys If the permanent longitudinal elongation exceeds 2-3%, and some aluminum lithium For alloys, permanent longitudinal elongation can exceed about 6-7%. As the length of the extrusion increases As time passes, the axial tensile force increases the stress state to or above the yield strength of the extrusion. held constant or changed in order to maintain This sets the axial tensile force. and in accordance with the requirement to maintain sufficient axial tensile force throughout the stretch forming operation. , a suitable measuring device for reacting the production mechanism, for example by hydraulic cylinder control. This can be achieved by installing control equipment and control equipment. Combined with molding work, specific 100 The combination of adding fractional axial elongation is the Poisson specific effect in the cross section. further improve tolerances by taking advantage of

Before and after the axial tensile force is applied to the extrudate, an external forming die 60 forms the outer periphery of the extrudate. It is connected to the surface part. The external forming die 60 is shaped to match the final desired cross-sectional shape of the extrusion. A working surface is provided. In some cases, the forming die is A surface is provided to overcompensate for the expected small-scale rebound that may occur. − In the preferred embodiment, the external forming die consists of two or more sections. These parts are located at or near one longitudinal end of the clamped extrusion. installed on the extrusion at a location, and suitable tightening is done by means of a device, e.g. to lock the dies together by a clamp, or a pneumatic or hydraulic clamp. tightened together. Some complex extrusions are made to accommodate complex cross-sectional shapes. Those skilled in the art will understand that multiple dissections may be required.

If the external forming die or extrusion is installed and the extrusion is under axial tension. , the external forming die can be used along the longitudinal length of the extrudate, in either direction, or in both directions. It is continuously advanced in the direction. The concept of die advancement is maintained under sufficient axial tension. It will be appreciated that extrudates include the use of fixed dies fed through the extrudates. cormorant. The die runs along a path that coincides with the longitudinal axis of the extrudate's tensile force. A traveling mechanism, such as a track-guided car, that is mounted on a It can be done. - In the preferred embodiment, the forming die has an axial tensile force applied along it. a traveling mechanism, or vehicle, that moves along a track that runs synchronously with a longitudinal axis , mounted on. Alternatively, coupled to one or more cables or dies, Thereby, the extrusion is formed by pulling the die along the longitudinal axis of the tensile force. It can be done like this. The die guide in the traveling mechanism prevents deviation from the die movement direction during forming. It was approved to ensure that it is kept to a minimum. Die movement speed can vary However, in an in-line extrusion process at speeds reaching approximately 60 m (200 ft) per minute, It has been found suitable to precede the speed of the extruder. 120m per minute The die speed reaching (400 ft) does not pose any disadvantage to the forming process based on theoretical evaluation. It has no beneficial effect. The working surface of the die acts to machine the outer wall of the extrusion. currently established by various U.S. and European industry associations, including the Aluminum Association. plastically deform aluminum extrusions within standard tolerances or better. Shape it. - In a preferred embodiment, the method of the invention is suitable for aluminum extrusions. Within less than half of the current standard tolerance established by the Aluminum Association for The finished extrusion is typically finished.

An external forming die such as the two-piece die 6o shown in FIG. 5 of the present invention has sufficient strength. and in the processing and reorientation of the extruded material. Sufficient lubricity must exist to allow plastic deformation. Made by Dai Typical die materials for use include steel alloys, zinc alloys, graphite-impregnated nylon and Contains certain epoxy die materials. However, it is not limited to these. Like The new die material is a cast zinc alloy sold under the trade name Kirksite.

The axial length of the die 60, as shown in FIG. must be sufficient. Die length is greater than approximately 1.27cm (0.5in) It has been recognized that the length of the tube is wide and can exceed about 30 cm (12 inches). multiple stages Multiple dies may be used in the present invention to form extrusions in stages. will be understood.

In one embodiment, the axial tensile force exerted on the extrusion is greater than the yield strength of the extrusion. It is made a little smaller, for example, 90% of the yield point. However, the production of molding dies moving forward For this purpose, the total axial tensile force to which the extrudate is exposed exceeds the yield point of the extrudate. as the extrusion or die to be formed is advanced. Suitable for being molded to match dimensions.

In one preferred embodiment of stretch forming, the die is free to move along the extrudate. Adequate lubricity should be present to allow local deformation of the extrudate to be carried out. . Such lubrication is accomplished, for example, through the use of certain epoxy materials or graphite. It can be provided within the die material through impregnation with materials such as. Alternatively, during from a thin film of lubricant of a certain weight, e.g. To the extruded part, a separate or automatically. Lubricating the die in the axial tension control system Reduces axial force fluctuations and improves surface appearance.

In one preferred embodiment, an internal forming die or hollow section of the extrusion may be used. Ru. Such internal dies are used to improve and strengthen the final dimensional tolerances of the extrusion. It can be used independently of or simultaneously with an external forming die for this purpose. a certain place In some cases, a combination of external and internal dies may be used to improve deformation. can be used in axial alignment with each other during molding. Internal molding die is closed the finished internal cross-sectional shape or dimensions of a closed or substantially closed extrusion substantially equal to.

Pull the internal forming die and thereby force the die into a passage aligned with the axis of the axial pull force. A cable mechanism is typically used to advance the die past the extrusion along the path. used.

In another embodiment, the hollow chamber of the elongated extrusion is formed by an external forming die or a feature of the extrusion. on the inner wall of the extrusion along a specified length of the extrusion as it is advanced along a specified length. Filled with fluid to apply equal pressure to both. such internal fluids and Pressure can be found, for example, in U.S. No. 4,704, the contents of which are incorporated herein by reference. No. 886, for example. However, the internal pressure in this example is intended to cause the treads of the hollow extrusion to bulge outward prior to advancement of the forming die. The outwardly bulging treads may be used for illustration purposes, and the outwardly bulging treads may later be used with external forming dies. Processed to fit within dimensional tolerances. Such pressure or deformation of extrusions If used to It is typically released prior to subsequent processing with a forming die.

Although the procedure of the present invention is typically performed at ambient temperature, in certain cases When using a constant alloy, the temperature is increased to maintain or change the temper during deformation. Taming can be carried out at reduced temperatures.

After the extrusion is formed under axial tension, the external forming die is opened and the tension or relaxation or vice versa, and the extrudate is removed from the device. Extruded products are be stretched and transferred within the time required to extrude the product to such lengths. It must be possible to Therefore, the method of the present invention is useful if desired. If so, it can be used as an in-line process for typical extrusion operations.

The stretch forming process of the present invention can be used simultaneously on multiple extrudates. such fruit In the example, a multi-extrusion product is one or more pieces, depending on the production equipment. is placed under axial tension and secured. Multi-extrusion products yield material Uniforms with polyacid boats when subjected to an axial tensile force greater than the strength External forming dies, which can be configured as taly die assemblies, are and move forward. Each die boat fits within such a boat while it is stretch-formed. It has a working surface that generally corresponds to the finished cross-sectional shape of the extrusion.

In another embodiment, an invention relating to stretch forming partially reshapes an extrudate. can be used for For example, certain extrusions may be limited by e.g. extrusion tooling. cannot be easily formed into the final desired shape by the field. Nevertheless, this invention According to the method, such desired shape is obtained by a stretch forming operation.

For example, Figure 7 shows a partial perspective view of an extrudate 80 that has a somewhat complex shape. 8th The figure shows the final desired shape for the extrusion 80 shown in FIG. such a final The desired shape is a die having a working surface that substantially matches the final desired cross-sectional shape of the extrudate. , while the extrudate is subjected to an axial tensile force exceeding the yield point of the extruded material. The extrusion is completed by advancing along the longitudinal axis. Like that Molding is a method for identifying extruded products whose final shape cannot be easily obtained by extrusion processes. End portions 82 and 84 are located in close proximity to each other along their lengths.

In addition to bringing the end portions 82,84 into close proximity, the stretch forming operation along with any other dimensional deviations that require correction, such as warping, twisting or bending. Make precise corrections.

Similarly, tensile forming methods can be used to form for forming extruded flanges where it is desired to create a pocket or storage tube. It can be used for

The present invention provides an in-line electrical-mechanical solution without creating significant residual stresses in the extrusion. A method for achieving consistent spatial dimensional modification of elongated extruded products by means of equipment provide. In any case, residual stresses generated by the stretch forming process Forces are typically generated by alternative local deformation operations and shape reorientation methods. smaller than the stress applied.

What is believed to be the best mode of the invention has been described above. illustrated Numerous changes may be made to the details described and described without departing from the scope of the invention. It will be clear to those skilled in the art that this can be done.

F I G, 4 FIG.5 F I G, 6 FIG.8 Procedural amendment (voluntary) May 1991)

Claims (7)

[Claims] 1. for at least a portion of an elongated metal extrusion, equal to the yield strength of said extrusion; or a process that exerts an axial tensile force sufficient to exceed An external forming die having a working surface substantially matching the finished cross-sectional shape of the extrudate is The process of applying it to the peripheral part of the side, with a total axial tensile force greater than or equal to the yield strength of the extrusion, The external forming die is placed under axial tension along a specific length of the extrusion in the extrusion direction. advancing an existing metal extrusion to form it; and The interior of the extrusion is applied with insufficient pressure to cause outward plastic deformation of the walls of the extrusion. The hollow interior of the extrusion is exposed to a fluid medium that exerts an even outward force around the part. process A method of forming an elongated metal extrusion having a 2. The method of claim 1, wherein the metal extrusion is aluminum. A method of forming elongated metal extrusions. 3. The method of claim 1, wherein an axial tensile force is applied to the extruded product. is an elongated metal extrusion resulting in a permanent elongation of at least 0.25% of the extrusion. How to form. 4. Finishing at least one elongated, thin-walled, hollow aluminum extrusion In the up-molding method: a step of solution heat treating the extrudate; mechanically gripping and retaining opposing longitudinal end portions of each elongated aluminum extrusion; The side of the extrudate is large enough to equal or exceed the yield point of the extrudate material. A longitudinal pull force of substantially equal tension across the cross section is applied to each extrusion and a small forcing the gripped end portion to produce a permanent elongation of at least 0.25%; During the pulling process, the length of the longitudinally moving forming die is at least 1.27 cm (0.5 cm). 5 in.) and generally match the finished cross-sectional shape for each extrusion. After the contact surfaces between the working surface and the extrusion surface have been lubricated, The process of bringing it into contact with the part, While maintaining controlled longitudinal tensile forces equal to or greater than the yield point of the extruded material. and between said gripped end portions along a path coinciding with the axis of longitudinal tension. advancing the forming die along substantially the entire length of each extrudate; a step of relaxing the longitudinal tensile force, a step of releasing the mechanical grip, and The process of moving each extrusion A method for finish forming a hollow aluminum extrusion having a 5. In a device for finish-forming elongated metal extrusions: the opposing length of each elongated metal extrusion a gripping device for gripping and holding the end portion in the hand direction; each extrusion to create sufficient axial tensile force to exceed the yield strength of each extrusion. means for forcibly pulling the gripped end of the item; An outer surface having a working surface that substantially matches the finished outer cross-sectional shape for each extrusion. A surface forming die that comes into contact with the peripheral part of the outer surface of the extruded product, metal extrusion advancing the external forming die along a specific length of each extrusion to form the article; and while the external forming die is advanced along a particular length of each extrudate; each extrusion with insufficient pressure to cause outward plastic deformation of the walls of each extrusion. A fluid medium within the hollow interior of the extrusion to exert an even outward force on the interior periphery. means to introduce A device for finishing forming elongated metal extrusions. 6. In a device for finish-forming elongated metal extrusions: the opposing length of each elongated metal extrusion a gripping device for gripping and holding the end portion in the hand direction; each extrusion to create sufficient axial tensile force to exceed the yield strength of each extrusion. means for forcibly pulling the gripped end of the item; An outer surface having a working surface that substantially matches the finished outer cross-sectional shape for each extrusion. A surface forming die that comes into contact with the peripheral part of the outer surface of the extruded product, metal extrusion advancing the external forming die along a specific length of each extrusion to form the article; means and with sufficient pressure to cause outward plastic deformation of the walls of each extrusion. inside the hollow interior of the extrusion to exert an even outward force on the interior periphery of each extrusion. and the external forming die along a specific length of each extrusion. means for releasing such outward forces before advancing A device for finishing forming elongated metal extrusions. 7. 7. The apparatus of claim 6, wherein opposite longitudinal end portions of the hollow extrusion Equipment for finishing forming elongated metal extrusions with seals.